It is generally known that transformers having a rated power of, for example, 100 MVA or higher at a rated voltage of 110 kV or higher are usually embodied as oil transformers, which can have a weight of up to 200 t. In this case, the transformer is arranged within an oil-filled transformer tank, wherein the oil serves both for insulation and for improved cooling. The electrical connection of the respective terminals of the transformer to outgoing line insulators on the outer side of the oil tank is in this case effected by means of electrical conductors which, if appropriate, are surrounded by a barrier system. A barrier system is constructed radially symmetrically around the relevant conductor and includes an electrically conductive screening pipe and, as necessary, a plurality of insulation barriers spaced apart from one another.
For reasons of mechanical stability, the conductors or the pipe-like barrier systems should be supported at specific distances within the oil tank. For this purpose, use is made, as necessary, of supporting insulators produced, for example, from pressboard material. The insulation capability of a solid supporting insulator is generally lower than the insulation capability of pure oil given an identical insulation path owing to the additional loading by creepage paths.
It is therefore disadvantageous that a required insulation clearance in the region of a supporting insulator is higher than if the conductor and the barrier system were floating freely in the oil, such that the oil tank has to be made larger than absolutely necessary. In addition, oil transformers of relatively high power and voltage are unique articles or are manufactured only in very small series, thus also resulting in a wide variety of geometrical requirements made of the supporting insulators, which leads to an undesirable diversity of variants, which ultimately necessitates an increased production outlay.